In known subscriber terminals for ISDN networks, the applications terminal that is connected through the socket connection, for example in the form of a PC, must be hardware- and software-adapted for this possibility of application. To that effect, such a PC must be equipped with an ISDN adapter card as well as a program diskette. Such an ISDN adapter card is relatively expensive. Until now, for example, only slow transmission was possible with the aid of "rate adaptation" e.g., when a PC was connected through a so-called external V24 interface. In addition, the PC control program stored on the diskette to enable the PC to communicate with the ISDN network, for example, was relatively costly and complicated. Furthermore, when using the subscriber terminal for different services such as telefax and telex, it is important that the respective applications terminal is always ready to operate, which can only be ensured when the respective applications terminal is permanently on line, i.e. day and night.